B737NG Cruise Alt and early return logic???
Here is the question:
Cruise altitude set in the pressurization controller is 400. After takeoff we see that we are too heavy for 400 for quite some time.
This is a 4 hour flight from Cancun to Denver.
So we request and get 380 as the final cruise altitude. My partner goes right ahead and sets 380 in the pressurization controller as we are climbing thru about 10,000 feet. I then seem to remember something about an "early return logic" where the pressurization will "know" the departure airport elevation in case we have to return to the field of departure. Remember that Denver landing altitude of 5450 is set in the LAND ALT window.
Two part question:
When does the logic witch over to my destination airport and what would happen if we returned to Cancun (at sea level) after setting 380 and without that early return logic being there anymore.
If one looks at the OFF SCHEDULE DESCENT QRH, it has you do nothing at all if you land at the airport of departure. Do you have to set zero in the case of Cancun or what happens when you touch down?